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Dermatology Flashcards

Approach to cases, revision, diagnostic sampling

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1
Q

What are the functions of the skin?

A
  • Protection
  • Production of glandular secretions
  • Sensory
  • Storage (fat)
  • Thermoregulation
  • Communication
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2
Q

What is the most common skin bacterial pathogen in the dog?

A

Staphylococcus pseudintermedius

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3
Q

What is the periople?

A

The band of soft rubbery horn over the perioplic dermis of the hoof, proximal to the coronary dermis

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4
Q

What points need to be established before treatment for a dermatological condition can be started?

A
  • What is happening to the skin

- Why this is happening, often secondary to a primary underlying cause (dermatological or systemic)

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5
Q

List the main diagnostic tests used when working up a dermatology case

A
  • Coat brushings
  • Skin scrapes
  • Skin cytology
  • Dermatophyte culture
  • Trichograms
  • Wood’s lamp examination
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6
Q

What tests may be required if the basic investigation of a dermatological disease does not give a diagnosis?

A
  • Blood tests
  • Skin biopsies
  • Microbial culture
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7
Q

What dermatological conditions are more likely in <1yo animals?

A
  • Immunologial immaturity
  • Demodicosis
  • Dermatophytosis
  • Juvenile pyoderma
  • Congenital defects
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8
Q

What dermatological conditions are more likely in <3yo animals?

A
  • Atopy
  • Follicular dyspasia
  • Keratinisation defects
  • Histiocytomas
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9
Q

What dermatological conditions are more likely in >6yo animals?

A
  • Hypothyroidism
  • Hyperadrenocorticism
  • Neoplasia
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10
Q

In an entire male with endocrine or dermatological changes, what is a key differential?

A

Testicular neoplasia producing/altering hormone production

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11
Q

What information do you need to know when working up a dermatology case?

A
  • When condition started
  • Details of in contact animals
  • lesions on people
  • How long owned
  • Housing and management
  • Travelled abroad
  • Past derm. history
  • Treatments given and response
  • Flea control
  • Exposure to potential sources of infection
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12
Q

What should be investigated in a clinical exam in the work up of a dermatology case?

A
  • Full clinical exam
  • Signs of systemic disease that may: underlie derm disease, affect diagnostic approach, affect treatment of skin
  • Signs associated with derm. disease e.g. lymphadenopathy with demodicosis, severe inflammation or lymphadenopathy from metastasis of skin neoplasm
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13
Q

Describe the dermatological examination when working up a dermatology case

A
  • Thorough and systematic: ears, interdigital spaces, claws, footpads, MMs,
  • Need good lighting and adequate restraint (sedation?) clip hair
  • Identify and record lesions and lesion groupings
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14
Q

What are the most common causes of dermatological disease?

A
  • Metabolic (incl. endocrine)
  • Neoplastic
  • Inflammatory
  • Immune mediated: hypersensitivities, auto-immune
  • Infectious: parasitic, bacterial, fungal, protozoal, viral
  • Traumatic
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15
Q

In what situations would you use unstained or stained acetate tape strips?

A
  • Stained: bacteria, yeasts, cytology

- Unstained: parasites e.g. surface mites

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16
Q

What are the advantages of in house tests for dermatology cases?

A
  • Rapid results while owner in practice
  • Provide diagnosis or rule out differentials
  • Specific and appropriate treatment can be prescribed
  • Reduce risk of unnecessary symptomatic treatment
  • Improved monitoring of the response to treatment
  • Cost effective to perform and improves practice income
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17
Q

What microscope objectives are best used for ectoparasites and hairs?

A

x4 and x10 objectives

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18
Q

What microscope objectives are best used for bacteria and yeasts, inflammatory and tissue cells?

A

x100 objective (oil)

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19
Q

What diagnostic tests are best for parasites?

A
  • Coat brushings
  • Coat combings (surface mites)
  • Acetate tape (unstained)
  • Skin scrapings (deep for Demodex, superficial for surface mites)
  • Plucks (demodicosis)
  • Biopsy
  • Examination of ear wax in liquid paraffin (Otodectes)
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20
Q

What diagnostic tests are best used for microbes?

A
  • Cytology (esp. bacteria and yeasts)
  • Bacterial culture: surface, fresh pustule, tissue biopsy optimal
  • Fungal culture (from hair plucks from lesion periphery, or McKenzie coat brushing)
  • Hair plucks examined under light microscope for dermatophytosis
  • Wood’s lamp for dermatophytosis
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21
Q

Outline the value of hair as a diagnostic sample for dermatological disease

A
  • Trichograms
  • pluck with haemostats, lie on liquid paraffin under coverslip
  • Also differentiation between alopecia as primary disease process, or due to self trauma
  • Self trauma indicated by broken distal tips
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22
Q

Describe the appearance of hair shafts affected by dermatophytosis

A

Covered with spores and penetrated by hyphae

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23
Q

What is the result of melanin clumping in hair?

A

Colour dilution alopecia

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24
Q

Outline the assessment of the hair bulb in a dermatology case

A
  • Assess to establish stage of hair growth
  • Telogen: hairs pear shaped, rough and non-pigmented, usually 80-90% of hairs, inactive and all hairs in telogen is suggestive of endocrinopathy
  • Anagen: bulbs rounded, smooth +/- pigmented centre, bulb may fold around shaft when plucked, actively growing hairs, normally 10-20% (poodles have more)
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25
Q

When should cytology be carried out with regards to dermatology cases?

A

In all dermatology cases

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26
Q

Give examples of cytology samples used in dermatology

A
  • Impression smears (erosions, ulcers, exudate, pustules, papules, indirect from biopsy)
  • Tape strips (crusts, scaling, alopecia, lichenification, erythematous skin)
  • Swab smears (transfer from swab to slide by rolling along surface)
  • FNA
  • Staining with DiffQuik
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27
Q

When should superficial skin scrapes be carried out?

A

All pruritic animals and scaling dermatosis

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28
Q

How many samples should be taken when performing skin scrapes?

A

3-5 sites should be scraped

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29
Q

What can be found on superficial skin scrapes?

A
  • Cheyletiella (usually dorsal aspect with scaling)
  • Notoedres cati
  • Otodectes cynotis usually preauricular skin, head, neck, tail base)
  • Trombicula autumnalis
  • Dermatophyte spores
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30
Q

When should deep skin scrapes be carried out?

A
  • In all cases of alopecia +/- pruritus
  • All cases of greasy skin
  • Comedones
  • crusting
  • Papules
  • Pustules
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31
Q

What can be found on deep skin scrapings?

A
  • Demodex

- Sarcoptes scabiei

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32
Q

Where and how many deep skin scrapes should be taken?

A
  • 3-5 sites
  • Demodex: edges of alopecic skin, comedones, erythema, papules, pustules, crusts, need to squeeze skin before scraping
  • Sarcoptes: ear margins, elbows, hocks, ventral abdomen, papules, crusted papules, untraumatised skin
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33
Q

What should you do if you are suspicious of Sarcoptes, but nothing is found on deep skin scrapings?

A

Prescribe 6-week diagnostic therapeutic trial, using selamectin or sarolaner

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34
Q

Explain the steps required in allergy workups

A

1: Rule out secondary infections and ectoparasites using other techniques
2: Rule in or out FAD, ultimate diagnosis depends on response to treatment
3: Rule in or out adverse food reaction by response to food trial and confirmation by challenging with suspected food
4: Clinical diagnosis of atopic dermatitis based on Favrot’s criteria, diagnosis of exclusion
- Serum and or intradermal allergy testing only following clinical diagnosis of atopic dermatitis once other causes of pruritus have been excluded

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35
Q

How many of Favrot’s criteria must be fulfilled to be diagnosed with atopic dermatitis?

A

5 of 8 need to be present

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36
Q

List Favrot’s criteria

A
  • Age of onset <3yo
  • Dog mostly indoors
  • Corticosteroid responsive
  • Chronic or recurrent yeast infection
  • Affected feet
  • Affected ear pinnae
  • Non-affected ear margins
  • Non-affected lumbosacral area
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37
Q

What actions should be taken if bacteria are found on cytology?

A
  • If coccid: treat or culture if chronic/recurrent

- If rods: always culture

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38
Q

What actions should be taken if Malassezia are found on cytology?

A

Treat (e.g. shampoos, anti-fungal treatment)

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39
Q

What actions should be taken if fungal hyphae and spores are found on cytology?

A

Culture

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40
Q

What actions should be taken if macrophages are found on cytology?

A

Culture and/or biopsy

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41
Q

What actions should be taken if round cells are found on cytology?

a: lymphocytes
b: histiocytes
c: mast cells

A

a: biopsy
b: possible histiocytoma, histopathology or could wait and see
c: excisional biopsy and histopathology

42
Q

When should skin biopsies be used?

A
  • To establish definitive diagnosis that cannot be reached by other, less invasive methods
  • Suspected neoplasm
  • Persistent ulceration/vesicular lesions
  • Skin disease unresponsive to rational treatment
  • Unusual or apparently serious disease, esp/ if animal unwell
  • Before using dangerous/expensive drugs
  • To rule out certain conditions
43
Q

What types of lesions are ideal for skin biopsy?

A
  • Early in disease to minimise chronic changes

- Primary lesion, mature lesion, multiple biopsies covering a range of lesions

44
Q

How should a skin biopsy for alopecia be taken?

A

Include normal skin and mark direction hair growth (wedge biopsy)

45
Q

How should a skin biopsy for ulcerated lesions be taken?

A

Include margin or normal and ulcerated skin (wedge biopsy)

46
Q

What are the basic structures in the skin?

A
  • Epidermis

- Dermis

47
Q

What are the layers in the epidermis, and in which order are they formed?

A

Starting at the deepest layer:

  • Stratum basale
  • Straum spinosum
  • Stratum granulosum
  • Stratum corneum
48
Q

Describe the changes that occur in keratinocytes as they move towards the surface

A

More keratin, polyhedral, become flattened and anuclear

49
Q

How are epidermal cells joined to each other?

A
  • Desmosomes and hemidesmosomes, tight junctions
  • Desmosomes: cell to cell
  • Hemidesmosomes: cell to protein
  • Tight junctions cell to cell
50
Q

What is the difference between a papule and a nodule?

A
  • papule is a small pimple/swelling on skin, often part of a rah, <1cm diameter
  • Nodule is small swelling or aggregation of cells in the body, esp. an abnormal one, >1cm diameter
51
Q

What is the difference between a macule and a patch?

A
  • Macule is an area of skin discolouration <1cm diameter

- Patch is a flat circumscribed area of discolouration >1cm,

52
Q

What is the difference between a vesicle and a bulla?

A
  • Vesicle is a small circumscribed elevation of epidermis containing clear fluid <1cm
  • Bulla is a large blister with serous fluid, >1cm diameter
53
Q

What is the difference between an erosion and an ulcer?

A
  • erosion is discontinnuty of the skin, exhibiting incomplete loss of epidermis, usually most, circumscribed and depressed
  • Ulcer is a sore on skin or a MM, accompanied by disintegration of tissue
54
Q

What is the difference between scale and crust?

A
  • Scale is the accumulation of loose fragments of the stratum corneum
  • Crust is a secondary lesion of dried exudate/serum/blood/medication/excessive scale on skin surface, or sequel to a pustule
55
Q

What is the difference between acanthosis and hyperkeratosis?

A
  • Acanthosis is diffuse epidermal hyperplasia, increased depth of epidermis, more layers
  • Hyperkeratosis is abnormal thickening of outer layer of skin, increased depth of cornified layer, more layers
56
Q

Name the major myiasis flies

A
  • Oestridae (bot and warble)
  • Sarcophagidae (flesh flies)
  • caliphoridae (blow, bottle flies)
  • Muscidae (some house flies)
57
Q

Name the major nuisance flies

A
  • House (Musca domestica and autumnalis)
  • Head flies (Hydrotaea irritans)
  • Stable flies (Stomoxys calcitrans)
  • Horn flies (Haematobia irritans)
58
Q

Name the dog lice and identify as chewing or sucking

A
  • Trichodected: chewing

- Linognathus: sucking

59
Q

Name the cat louse and identify as chewing or sucking

A

Felicola, chewing

60
Q

Name the horse lice and identify as chewing or sucking

A
  • Damalinia: chewing

- Haematopinus: sucking

61
Q

Name the cow lice and identify as chewing or sucking

A
  • Damalinia: chewing

- Haematopinus, Linognathus: sucking

62
Q

Name the sheep and goat lice and identify as chewing or sucking

A
  • Damalinia: chewing

- Linognathus: sucking

63
Q

Name the pig louse and identify as chewing or sucking

A

Haematopinus suis: sucking

64
Q

Name the poultry lice and identify as chewing or sucking

A
  • Lipeurus
  • Cuclogaster
  • Menacanthus
  • All chewing
65
Q

Name the guinea pig lice and identify as chewing or sucking

A
  • Gliricola
  • Gyropus
  • Both chewing
66
Q

Name the dog surface mites

A
  • Cheletiella yasurgi
  • Otodectes cynotis
  • Trombicula autumnalis
67
Q

Name the dog deep mites

A
  • Sarcoptes scabiei

- Demodex

68
Q

Name the cat surface mites

A
  • Cheyletiella blakei
  • Otodectes cynotis
  • Trombicula autumnalis
69
Q

Name the cat deep mite

A

Notoedres cati

70
Q

Name the horse surface mites

A
  • Psoroptes equi

- Chorioptes bovis

71
Q

Name the horse, cow, sheep and pig deep mite

A

Sarcoptes

72
Q

Name the cow surface mites

A
  • Psoroptes ovis

- Chorioptes bovis

73
Q

Name the sheep surface mite

A

Psoroptes ovis

74
Q

Name the pig surface mite

A

Psoroptes suis

75
Q

Name the poultry surface mites

A
  • Dermanyssus

- Ornithonyssus

76
Q

Name the poultry deep mite

A

Knemidocoptes

77
Q

Name the rabbit surface mites

A
  • Cheyletiella parasitivorax
  • Psoroptes cuniculi
  • Listrophorus
78
Q

Name the guinea pig surface mite

A

Chirodiscoides

79
Q

Name the guinea pig deep mite

A

Trixicarus cavidae

80
Q

Compare the appearance of Ixodes, Dermacentor and Rhipicephalus ticks

A
  • Ixodes: large mouthparts, inornate, no festoons, anal groove in front of anus
  • Dermacentor: eyes present, palpi wider than long, ornate, festoones, basis capituli rectangular, anal groove below anus and U shaped
  • Rhipicephalus: eyes present, palpi wider than long, inornate, festoons, basis capituli hexagonal, anal groove below anus and wine glass shaped
81
Q

Give examples, activity against G+ve and G-ve, pseudomonas, and whether bacteriostatic or bactericidal for beta-lactam antibiotics

A
  • Amoxicillin clavulanate, cephalezin, cefoveci
  • Active against G+ve and -ve
  • No activity against Pseudomonas
  • Bactericidal
82
Q

Give an example, activity against G+ve and G-ve, pseudomonas, and whether bacteriostatic or bactericidal for macrolide antibiotics

A
  • Clindamycin
  • Active against G+ve, G-ve intrinsic resistance
  • No acitivyt against Pseudomonas
  • Bacteristatic
83
Q

Give examples, activity against G+ve and G-ve, pseudomonas, and whether bacteriostatic or bactericidal for potentiated sulphonamide antibiotics

A
  • TMPS
  • Active against G+ve and -ve
  • No activity against Pseudomonas
  • Bactericidal
84
Q

Give examples, activity against G+ve and G-ve, pseudomonas, and whether bacteriostatic or bactericidal for fluroquinolone antibiotics

A
  • Enrofloxacin, marbofloxacin, pradofloxacin, orbifloxacin
  • Active against G+ve and G-ve
  • Active against Pseudomonas
  • Bacteristatic
85
Q

Give examples, activity against G+ve and G-ve, pseudomonas, and whether bacteriostatic or bactericidal for aminoglycoside antibiotics

A
  • Gentamycin, framycetin, fusidic acid, polymixinB
  • Active against G+ve: only framycetin and fusidic acid
  • Active againse G-ve: only gentamycin, framycetin, polymixin B
  • Active against Pseudomonas: genta fram, polymixin B
  • All but fusidic acid are bactericidal
86
Q

Key points on type I hypersensitivities

A
  • Rapid, 15-20 mins
  • Sensitised individuals
  • Mast cell bound IgE cross links, degranulate, release of bioactive molecules
  • Oedema, inflammation, bronchoconstriction, pruritus
87
Q

Key points on type II hypersentivities

A
  • Target cell destroyed by binding of IgG or IgM to cell surface antigen
  • Cytolysis due to complement or NK cells or target phagocytosed by macrophage
  • Ab recognises self antigen on host or tissue cell, or Ab recognises small molecuels attached to cell or tissue
  • E.g. thrombocytopaenia, haemolytica anaemia, myasthenia gravis
88
Q

Key points on type III hypersensitivity

A
  • Reaction ~4-8hrs
  • Immune complex mediated
  • Deposition of Ab/Ag complexes in vessels or tissues, escape normal clearance
  • Ab or Ag excess
  • Ag soluble, endo or exogenous source
  • Localised reaction = Arthus reaction
  • Allergy to fugal spores in cattle, recurret airway obstruction in horses, blue eye and Leishmaniasis in dogs
  • Also SLE, polyarthritis, nephritis
89
Q

Key points on type IV hypersensitivities

A
  • Delayed type, within 24-72 hours
  • T cell mediated, interaction between dendritic and primed T cells
  • T recognise Ag, recruit and activate mononuclear cells via IFNy and chemokines
  • HEvs form, upregulation of vascular adressins
  • Inflammation at site of interaction
  • Tuberculin reaction in skin, granuloma formation e.g. pemphigus foliaceous
90
Q

Explain the significance of finding bacilli on cytology for a dermatology case

A
  • Unless suspect faecal contamination, need to carry out bacterial culture and sensitivity where possible
  • May indicate Pseudomonas, which are frequently resistant to antibiotics
91
Q

Describe the appearance of degenerating neutrophils

A
  • Nuclei lose lobulaion

- Nuclei swell

92
Q

What is indicated by a cytology sample with;

a: >70% granulocytes present?
b: >50% monocytes present?
c: mixture of neutrophils and macrophages?

A

a: Acute inflammation
b: chronic inflammation
c: pyogranulomatous inflammation

93
Q

What is required in order to confirm whether a pustule/inflammatory lesion is truly sterile?

A

Must carry out culture - easy to get false negatives, esp. with pyogranulomatous inflammation

94
Q

What does finding nucleated keratinocytes on cytology indicate?

A
  • Can indicate more rapid epidermal turnover e.g. inflammation
  • Also a specifi c feature of certain diseases causing parakeratotic hyperkeratosis (e.g. zinc deficiency, hepatocutaneous syndrome)
95
Q

Describe the appearance of epithelial granules

A
  • Within epithelial cells only

- tend to stain lighter/brown vs basophilic bacteria

96
Q

What causes the appearance of nuclear chromatin streaks?

A

From ruptured cells

97
Q

What information can be gained from Trichograms?

A
  • Presence of Demodex, lice, Cheyletiella eggs
  • Presence of dermatophytes on shaft (low sensitivity)
  • Anagen/telogen bulbs, shaft/tip abnormalities
98
Q

Explain why skin biopsy is particularly useful in Shar Peis

A

Skin may be too thick and lead to false negatives on skin scrapes, so biopsy may be needed for detection of demodicosis

99
Q

Outline the requirements for skin biopsy

A
  • Sample representative of lesion
  • Multiple samples if possible (min. 3)
  • Sample fully developed lesions where possible
  • Alopecia: biopsy max hair loss, margin to normal and normal haired skin
  • Ulcerated: ulcerated area and area just adjacent, where epidermis still in tact
  • Pustules, vesicles, bullae: remove whole lesion without disruption
100
Q

State whether incisional or excisional biopsy would be most appropriate for the following lesions:

a: excision of soitary nodule
b: vesicles
c: transition between normal and lesional skin e.g. alopecia, ulceration edges
d: biopsy of cutaneous masses
e: suspected deep lesions e.g. panniculitis

A

a: Excisional
b: Excisional (less likely to damage than a punch)
c: Incisional
d: Incisional
e: Incisional

Dermatology 2 (23 decks)

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